Phil of SAS helped me identify this function. Thank you.
T-test conducted in PROC GLIMMIX (or most likely other regression procedures) is expressed in Excel function as:
=2*(1-T.DIST( T_VALUE , DEG_OF_FREEDOM ,TRUE))
where T_value must be an absolute value of the original t-value (e.g., if -2 then 2).
This expresses CDF (cumulative distribution function), not PDF (probability density function). I will explicitly discuss what these are in the near future.
I wanted to know how much of statistical results (off PROC GLIMMIX in this case) comes from SAS's internal computation (i.e., I can't replicate results outside SAS) and how much of it can be done in Excel given what I get from SAS output.